Transient event detector circuit and method

ABSTRACT

Disclosed examples include a transient event detector circuit to detect transient events in a switching converter, including a DLL circuit to detect changes in a duty cycle of a pulse width modulation signal used to operate a switching converter, and an output circuit to provide a status output signal in a first state when no transient event is detected, and to provide the status output signal in a second state indicating a transient event in the switching converter in response to a detected change in the duty cycle of the pulse width modulation signal.

BACKGROUND

Switching converters are used to convert electrical power from one formto another by operation of a switching circuit. Examples include DC-DCswitching converters with switch circuits to convert DC input power intoa controlled DC output to drive a load. Single-phase systems include asingle switching converter to drive the load. Multiphase systems includetwo or more switching converters connected in parallel with one anotherto provide a regulated output voltage, with the ability to activate ordeactivate certain switching converters depending on load currentrequirements. In single or multiphase switching converter systems, it isdesirable to react to transient conditions, such as line or loadvariations. For example, changes in load current requirements may allowone or more phases to be turned off or disabled to enhance overallsystem energy efficiency. Other changing conditions may requireactivation of one or more phases to accommodate increased load currentrequirements. Changing input power conditions, such as variations ininput voltage levels can likewise be accommodated by selectivelyactivating or deactivating phases of a multiphase system. Using parallelinductors at the outputs of individual switching converter phases canimprove transient response, but this might lead to energy inefficienciesin steady state operation. It is then a great advantage to detect asfast as possible the transient event and to know when the system wentback to steady state. Transient events are typically short and detectingcertain events requires very high-speed circuitry, leading to cost andenergy efficiency challenges in switching converter design. Enhancedefficiency and intelligent phase management can be facilitated by fastdetection of transient events and also fast notification that the systemhas returned to steady state operation.

SUMMARY

Disclosed examples include power conversion systems, integrated circuitsand transient event detector circuits to detect transient events inswitching converters. The transient event detector circuit in certainexamples includes a delay lock loop (DLL) circuit to detect changes in aduty cycle of a pulse width modulation (PWM) signal used to operate aswitching converter. The detector circuit provides a status outputsignal in a first state when no transient event is detected. Thedetector circuit provides the status output signal in a second stateindicating a transient event in the switching converter in response to adetected change in the duty cycle of the PWM signal. The DLL circuit inone example includes a monostable multivibrator to generate a pulseoutput signal triggered by a first edge of the PWM signal, as well as aphase detector to provide first and second output signals according to aphase difference between the second edge of the PWM signal and acontrolled edge of the multivibrator pulse output signal. A charge pumpselectively sources or sinks current to or from a capacitor according tothe phase detector outputs to establish a voltage control signal. Thecapacitor provides the voltage control signal as a control input to themultivibrator to align the second edges of the multivibrator pulseoutput and PWM signals. In certain examples, the DLL circuit has abandwidth equal to the bandwidth of a control circuit operating theswitching converter so that both systems are over-slewed for the sametype of transient events. This facilitates detection that a previoussteady state duty cycle has changed within the PWM cycle in which thechange occurs. Fast transient detection, in turn, facilitates timelyintelligent adjustments in single and/or multiphase switching convertersystems, such as selectively activating or deactivating one or morephases in a multiphase system. In certain examples, the transient eventdetector circuit filters the phase detector output signals, andgenerates the status output signal according to the filtered phasedetector signals. The first and second filtered phase detector signalscan also be provided as output signals to distinguish between positiveand negative transient events. The transient event detector circuit incertain examples is provided in a switching controller integratedcircuit (IC) along with a control circuit to operate the switchingconverter. In other examples, the transient event detector circuit isintegrated with a multiphase converter master controller that receivesPWM signals from one or more individual switching converter controlcircuits to identify a load and/or line transient event based on changesin PWM signal duty cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a transient event detector circuit witha DLL to detect changes in a PWM signal duty cycle.

FIG. 2 is a schematic diagram of a monostable multivibrator in the DLLof FIG. 1.

FIG. 3 is a schematic diagram of a switching converter controller ICwith a transient event detector circuit in a multiphase power conversionsystem.

FIG. 4 is a waveform diagram showing various signals in the circuits ofFIGS. 1-3.

FIG. 5 is a system diagram of a multiphase power conversion system witha transient event detector providing signals to a master controller.

FIG. 6 is a system diagram of a multiphase power conversion system witha master controller including a transient event detector circuit.

DETAILED DESCRIPTION

In the drawings, like reference numerals refer to like elementsthroughout, and the various features are not necessarily drawn to scale.In the following discussion and in the claims, the terms “including”,“includes”, “having”, “has”, “with”, or variants thereof are intended tobe inclusive in a manner similar to the term “comprising”, and thusshould be interpreted to mean “including, but not limited to . . . ”.Also, the terms “couple”, “couples”, or “coupled” are intended toinclude indirect or direct electrical or mechanical connection orcombinations thereof. For example, if a first device couples to or iscoupled with a second device, that connection may be through a directelectrical connection, or through an indirect electrical connection viaone or more intervening devices and connections.

FIG. 1 shows a transient event detector circuit 100 including an input102 that receives a first signal PWM from a switching converter controlcircuit, referred to herein as a pulse width modulation signal PWM. Thetransient event detector circuit 100 also includes signal outputs 142,144 and 146 that provide a status output signal SS, a positive transientsignal TR+ and a negative transient signal TR−, respectively. Thecircuit 100 can be used in any form of power conversion system thatincludes one or more switching converter stages to convert power fromone form to another. Disclosed examples are illustrated and describedbelow in connection with DC-DC switching converters, although theconcepts of the present disclosure are not limited to the illustratedexamples. In operation, the switching converter operates according tothe PWM signal, and the circuit 100 quickly detects that a previoussteady state duty cycle of the PWM signal has changed within the cyclein which the change occurs. The circuit 100 provides a solution toquickly identify transient events at the input and/or output of aswitching converter, allowing timely intelligent responsive measures.For example, one or more of the outputs SS, TR+ and TR− can be used byconverter control circuitry for intelligent load management for enablingor disabling individual switching converter phases in a multiphase powerconversion system in response to a line or load transient event.

The transient event detector circuit 100 includes a delay lock loop(DLL) circuit formed by a monostable multivibrator circuit 110, a phasedetector circuit 120 and a charge pump circuit 130. The received firstsignal PWM can be generated by any suitable source, such as controlcircuitry operating a DC-DC converter circuit. The signal PWM has arising edge, a falling edge, and a duty cycle representing an on time ofa switching device of the associated switching converter in a givenconverter switching cycle. The monostable multivibrator circuit 110includes a signal input 102 that receives the signal PWM, and an output114 that generates a pulse output signal TIMER with a first edgetriggered by a first edge of the PWM signal. In the illustrated example,the monostable multivibrator circuit 110 provides the output pulsesignal TIMER having a rising edge triggered by the rising edge of thePWM signal. The second (e.g., falling) edge of the pulse output signalTIMER is controlled by a voltage control signal VCTRL received at acontrol input 112 of the multivibrator 110.

The phase detector circuit 120 includes a first input inverter 116 thatreceives the TIMER signal and provides an inverted signal TIMER′ at anoutput 118. A second inverter 117 is provided at a second input of thephase detector 120. The inverter 117 receives the PWM signal andprovides an inverted signal PWM′ at an output 119. The phase detector120 includes first and second outputs 128A and 128B to provide first andsecond output signals UP and DOWN according to a phase differencebetween the second edge of the PWM signal and the controlled second edgeof the multivibrator pulse output signal TIMER. The output 118 of theinverter 116 provides the inverted signal TIMER′ to a clock input of afirst data (D) flip-flop 122. A second D flip-flop 124 has a clock inputthat receives the inverted first signal PWM′. The data inputs “D” of theflip-flops 122 and 124 are connected to a supply voltage VDD (logic highin this example). The output 128A of the first flip-flop 122 (“Q”flip-flop output) provides a first phase detector output signal UP in afirst state (e.g., high) in response to the falling edge of the outputpulse signal TIMER. The “Q” output of the second flip-flop 124 isconnected to a second output 128B of the phase detector 120. The output128B provides a second phase detector output signal DOWN in a firststate (e.g., high) in response to the falling edge of the first signalPWM. The flip-flops 122 and 124 in FIG. 1 are reset by the active lowoutput of a NAND gate 126, whose inputs are connected to the flip-flopoutputs 128A and 128B.

In this configuration, the phase detector 120 provides an UP signal inan active first state (high) in response to the falling edge (secondedge) of the PWM signal lagging the falling edge of the TIMER signal.The UP signal in this example has a rising edge triggered by the fallingedge of the TIMER signal, and a falling edge triggered by the receipt ofa lagging PWM signal falling edge. The phase detector 120 provides theDOWN signal in this example in an active (high) first state in responseto the falling edge of the PWM signal leading the falling edge of theTIMER signal. The resulting DOWN signal has a rising edge triggered bythe falling edge of the PWM signal, and a falling edge triggered byreceipt of a lagging TIMER signal falling edge. In steady stateoperation, the second edges of the TIMER and PWM signals will bealigned, and the UP and DOWN signals will both be generally inactive(low) apart from intermittent glitches. Any change in the duty cycle ofthe PWM signal, however, will be detected by the circuit 100, in whichcase the first and second phase detector output signals UP and DOWN aregenerated according to any phase difference between the falling edges ofthe PWM and TIMER signals.

The charge pump circuit 130 selectively sources or sinks current to orfrom a capacitor C1 according to the UP and DOWN signals to establishthe voltage control signal VCTRL at the multivibrator control input 112.The multivibrator 110 provides a feedback path according to the voltagecontrol signal VCTRL to adjust the duration of the TIMER pulses in orderto align the second edges of the TIMER and PWM signals. The charge pumpcircuit 130 includes a first switching circuit 134 that operates whenthe UP signal is high to connect a first current source 131 to thecontrol input 112 to source a first current I1 to the capacitor C1. Thecurrent source 131 is connected between a first analog supply referencevoltage VDDA and the switching circuit 134. A second switching circuit136 selectively connects a second current source 132 to the controlinput 112 to sink a second current (e.g., also I1 in this example) fromthe capacitor C1 when the second phase detector output signal DOWN ishigh. The second current source 132 is connected between the switchingcircuit 136 and a second analog supply reference voltage VSSA. The firstand second currents are equal in one example, both having a valuelabeled I1 in FIG. 1.

An output circuit 140 provides the status output signal SS at the output142 in a first state (high) when neither of the first and second phasedetector output signals UP, DOWN is in the first state (high). When oneof the first and second phase detector output signals UP or DOWN isactive (high), the output circuit 140 provides the status output signalSS in a second state (low) indicating a transient event in theassociated switching converter. The output circuit 140 in FIG. 1 filtersthe UP and DOWN signals to generate the status output signal SS. A firstlow pass filter circuit is formed by a resistor RF1 and a capacitor CF1chosen to have a time constant of a few nanoseconds in one example. Thefirst filter circuit RF1, CF1 receives the UP signal from the phasedetector output 128A and includes an output 144 to provide a firstfiltered output signal TR+ having a first state (high) when the firstphase detector output signal UP is high for a sufficient amount of time.The output circuit 140 also includes a second low pass filter circuitRF2, CF2, including an input coupled with the phase detector output 128Bto receive the second phase detector output signal DOWN. An output 146of the second filter circuit provides a second filtered output signalTR− having a first state (high) when the second phase detector outputsignal DOWN is high for a sufficient amount of time according to thetime constant of the filter circuit RF2, CF2. The output circuit 140 inthis example also includes a NOR gate 141 with a first input coupledwith the output 144 of the first low pass filter circuit RF1, CF1 and asecond input coupled with the output 146 of the second low pass filtercircuit RF2, CF2. The output 142 of the NOR gate provides the statusoutput signal SS in the first state (high) when neither of the signalsTR+, TR− is high to indicate steady state operation of the associatedswitching converter. The NOR gate 141 provides the status output signalSS in a second state (low) indicating a transient event in the switchingconverter when one of the first and second filtered output signals TR+,TR− is high.

FIG. 2 shows an example monostable multivibrator circuit 110 which canbe used in the transient event detector circuit 100 of FIG. 1. Themultivibrator circuit 110 includes a D flip-flop 200 with a clock input202 that receives the PWM signal from the transient detector input 102.The flip-flop 200 provides a normal data output signal “Q” at an output204, and an inverted output “Q′” at a second output 206. A reset input(RST) of the flip-flop 200 is driven by the TIMER signal on line 208from the output 114 of the monostable multivibrator circuit 110. Thecircuit 110 also includes a comparator circuit 210 connected between theanalog supply voltage node VDDA at line 212 and the second analog supplyVSSA at line 214. The control voltage signal VCTRL is provided to afirst comparator input 216. A CMOS input stage including transistors M2and M3 receives the voltage control signal VCTRL, and the correspondingCMOS circuit output node 218 is connected to gate terminals of PMOStransistors M4 and M5 and to the gates of NMOS transistors M6 and M7. Afirst switch 221 is connected between the node 218 and VSSA and operatesaccording to the Q′ signal to reset the control input side of thecomparator circuit 210. The comparator circuit 210 includes a secondinput node 220 connected to VDDA through a switch 223 and a resistor R.The switch 223 operates according to the Q signal from the flip-flop 200to selectively deliver charging current to the second input node 220. Amultivibrator capacitor C2 is connected between the second input node220 and VSSA to control the voltage at the node 220. A switch 222 isconnected between the node 220 and VSSA in parallel with the capacitorC2. The switch 222 operates according to the Q′ signal to discharge thecapacitor C2 to reset the voltage at the second input node 220. Thevoltage across C2 is provided as a gate control signal to a CMOS outputformed by a PMOS transistor M8 and an NMOS transistor M9 connectedbetween M5 and M7. The output transistor pair M8 and M9 have drainsconnected to an output node 224 that provides an input signal to a NORgate 226. The Q′ signal is provided to the other input of the gate 226,and the output of the gate 226 provides the TIMER signal at themultivibrator output 114.

After the comparator circuit 210 is reset by the switches 221 and 222,the next rising edge of the signal PWM causes the flip-flop Q signal togo high, and the Q′ signal to go low. In this state, the switch 223allows current flow through the resistor R to charge the capacitor C2until the voltage at the node 220 turns on M9 to bring the voltage atthe NOR gate input 224 low. The output of the NOR gate 226 goes high,causing a rising edge in the TIMER signal at the multivibrator output114. The high state of the TIMER signal resets the flip-flop 200,causing the Q signal to again go low, and the Q′ signal to go high. Thisresets the comparator circuit 210 by closing the switches 221 and 222,and opening the switch 223. The multivibrator circuit 110 controls thepulse width of the TIMER output signal according to the level of thevoltage control signal VCTRL. In closed loop operation of the DLLcircuit of FIG. 1, reducing the voltage control signal VCTRL reduces theTIMER signal pulse width or pulse duration because less time is requiredto charge the capacitor C2 to the corresponding level set by VCTRL inthe multivibrator circuit 110. Conversely, increasing VCTRL allows thecapacitor C2 to charge for a longer time, and thus increases theduration of the TIMER signal pulses.

The example circuit 100 of FIGS. 1 and 2 compares falling edges of theTIMER and PWM signals. In other examples, rising edge comparisons can beused by a corresponding phase detector circuit 120. In other examples, aphase comparator can compare a rising edge of one of the signals TIMER,PWM with a falling edge of the other signal in order to selectivelyprovide an output signal based on a phase difference between thecompared edges. The circuit 100 in FIG. 1 uses a voltage controlledmonostable multivibrator circuit 110 and a feedback loop to implement aDLL in which the output of the variable monostable circuit 110 tracksthe duty cycle of the PWM signal. The status signal SS can be used by ahost circuit to identify changes in the PWM signal duty cycle, andthereby detect load or line transient events in a correspondingswitching converter. In this example, if the switching converter reactsto a transient event through normal close loop PWM regulation of itsoutput signal, the duty cycle of the corresponding PWM signal willchange, and this duty cycle change is reflected by either the UP or theDOWN signal within the same PWM control cycle during which the transientevent occurred. In certain implementations, the DLL circuit 110, 120,130 has a bandwidth equal to the bandwidth of a control circuitoperating the corresponding switching converter. This enhances transientevent detection by ensuring that the controlled switching converter andthe DLL become similarly over-slewed for the same type of detectabletransient events.

FIG. 3 shows an example power conversion system 300 in which thetransient event detector circuit 100 can be used in combination with acontrolled DC-DC switching converter 320 and an associated convertercontrol circuit 302. As seen above, a host system can use the statussignal SS to create a transient event flag to initiate appropriateresponsive action in the system 300. In addition, the TR+ and TR−signals provided at the circuit outputs 144 and 146 can also be used todistinguish between positive and negative transient events. In theexample of FIG. 3, an integer number N DC-DC switching converters 320are used to drive a single load 330 with a regulated output voltage VO,where N is greater than 1. A multiphase converter master controllercircuit 340 uses the SS, TR+ and TR− signals to selectively enable ordisable certain of the switching converters 320 using correspondingslave control signals SCL1, SCL2, . . . , SCLN. In this example, thecontrol circuit 302 that operates one of the DC-DC switching converters320 is included along with the transient event detector circuit 100 in asingle integrated circuit (IC) 301. The circuit 100 of FIG. 1 can beused in combination with a variety of different DC-DC converter systems.FIG. 3 shows an example multiphase buck DC-DC converter system 300 witha DC-DC converter circuit 320, and the system 300 includes one or moreadditional converter circuits 320 (not shown in FIG. 3).

The system 300 includes a PWM controller integrated circuit (IC) 301with a transient event detector circuit 100 as described above thatreceives a PWM signal at an input 102 from the control circuit 302, andprovides the signals SS, TR+ and TR− to the master controller 340. Thecontrol circuit 302 implements closed loop voltage control of the outputvoltage VO to deliver current IO to a load 330. The control circuit 302in this example includes a modulator circuit 304 that generates thepulse width modulation signal PWM according to one or more feedbacksignals IFB, VFB to regulate the output voltage signal VO by generatingswitching control signal SC1 and SC2 according to the signal PWM. In theillustrated buck converter example, the modulator 304 generates thefirst switching control signal SC1 by providing a signal to a firstdriver circuit 306 generally according to the PWM signal, and generatesthe low side switching control signal SC2 via a second driver circuit308 according to the inverse of the PWM signal. The drivers 306 and 308respectively provide first and second switching control signals SC1 andSC2 at IC outputs 314 and 316 to operate high and low side switches S1and S2 of the DC-DC switching converter 320. The modulator circuit 304includes an output 305 that provides the PWM signal to the input 102 ofthe transient detector circuit 100 as described above. The controlcircuit 302 includes a first comparator 310 that compares a voltagereference signal VR to a feedback voltage signal VFB from an IC input319 for regulating the output voltage VO of the DC-DC converter 320. Inaddition, a second comparator 312 compares a current threshold ITH witha current feedback signal IFB received at an IC input 318 from the DC-DCconverter circuit 320. The DC-DC converter switching devices S1 and S2operate according to the switching control signals SC1 and SC2 toconvert DC input voltage VIN to provide a controlled DC output voltageVO to drive the load 330.

The first or high side converter switching device S1 is coupled betweenan input voltage node 322 and a switching node 326. The second switchingdevice S2 is connected between the switching node 326 and an outputreference voltage node 324 (labeled GND in the drawing). An outputinductor L is connected between the switching node 326 and an outputnode 328. An output capacitor CO is connected between the output node328 and the reference voltage node 324. A resistive divider networkprovides the voltage feedback signal VFB to the comparator 310 as avoltage in a node joining resistors R1 and R2 connected in series withone another in parallel with the output capacitor CO. In operation, thecontrol circuit 302 provides alternating pulse width modulated switchingcontrol signals SC1 and SC2 in order to turn on S1 to magnetize theinductor L, and then to turn S1 off while turning on S2 in CCM operationfor relatively high output current requirements. The inductor L conductscurrent IL from the switching node 326 to charge the output capacitorCO. Turning on S2 allows current to flow through the inductor L and theoutput capacitor CO, with the alternate operation of S1 and S2maintaining a regulating the output voltage VO across the capacitor CO.A current sensor senses the inductor current IL to provide the currentfeedback signal IFB to the IC input 318 for comparison with a thresholdITH via the comparator 312. Controlled operation of the convertercircuit 320 drives the load 330 with output current IO.

Referring also to FIG. 4, a waveform diagram 400 illustrates varioussignals in the DC-DC converter system 300 of FIG. 3 and the transientevent detector circuit 100 of FIG. 1. The PWM signal is shown as curve410 including a first (e.g., rising) edge 410 a and a second (falling)edge 410 b. In this example, the PWM signal begins with a rising edge ineach of a series of PWM cycles having a cycle period TPWM. Themonostable multivibrator output pulse signal TIMER is shown as curve 420including a first (e.g., rising) edge 420 a triggered by the first edge410 a of the pulse with modulation signal PWM, and a second (falling)edge 420 b controlled by the multivibrator circuit 110 to set the pulseduration TMS of the pulse output signal TIMER according to the voltagecontrol signal VCTRL. Curves 430 and 440 respectively show the first andsecond switching control signals SC1 and SC2 in the switching converter320. In this example, an output load current requirement of theswitching converter 320 is shown as a curve 450 that varies as afunction of time t. A curve 460 shows the status output signal SSremaining in the first state (high) and providing low going pulses attimes T1, T2, T3, T4 and T5 based on the circuit 100 detecting transientevents according to duty cycle changes in the PWM signal. The positivetransient event signal TR+ is shown as curve 470 and the negativetransient event signal TR− is shown as curve 480.

Between the illustrated times T0 and T1, the output current IOrequirement curve 450 is generally constant, and the PWM signal curve410 accordingly provides a generally constant duty cycle (e.g.,approximately 50% in this example). The TIMER signal curve 420 generallytracks the PWM signal curve 410 in the steady state operation between T0and T1, and the switching control signal curves 430 and 440 generallytrack the PWM signal 410 by operation of the control circuit 302. Justprior to T1, the output current requirement curve 450 increases, causingthe control circuit 302 to extend the duty cycle of the PWM signal. AtT1, the circuit 100 detects that the falling edge of the PWM signal lagsthe falling edge of the TIMER signal, causing assertion of the UP signalat the phase detector output 128A (FIG. 1). The output circuit 140filters the UP signal, and the resulting filtered signal is provided asa high-going pulse in the TR+ signal curve 470. This TR+ signal pulseswitches the output of the NOR gate 141, which provides a low-goingpulse in the status output signal SS in curve 460. The output currentrequirement curve 450 remains generally high between T1 and T2, and theclosed loop operation of the switching converter control circuit 302controls the on-time TON1 of the first switching device S1 and theon-time TON2 of S2 according to the PWM signal curve 410.

At time T2, the output current requirement 10 decreases, causing acorresponding decrease in the PWM signal duty cycle by operation of thecontrol circuit 302. The phase detector circuit 120 asserts the DOWNsignal in response to detection of the falling edge 410 b of the PWMsignal leading the falling edge 420 b of the TIMER signal. This createsa high-going pulse in the DOWN signal, which is filtered and provided asa high-going pulse in the TR− curve 480. The TR− pulse switches the NORgate output 142 which provides another low-going pulse in the SS signalcurve 460 to indicate detection of a transient condition in the powerconverter 320. A further decrease in the output current requirement atT3 causes the transient event detector circuit 100 to generate anotherlow-going pulse in the SS curve 460 and a corresponding high-going pulsein the TR− curve 480. In this example, the current requirement undergoesa further decrease at T4, leading to further pulses in the SS andTR-curves 460 and 480, respectively. Prior to time T5 in FIG. 4, theoutput load current requirement increases, which causes a further phasedifference between the PWM and TIMER signals. In this increasing loadcurrent instance, the falling edge of the TIMER signal leads thecorresponding falling edge of the PWM signal, and the transient detectorcircuit 100 generates a low-going pulse in the SS signal curve 460 alongwith a corresponding high-going pulse in the TR+ curve 470.

As seen above, the transient event detector circuit 100 advantageouslyprovides one or more signals SS, TR+, TR− to indicate to a host systemthe occurrence of a transient event associated with a switchingconverter 320. In addition, the circuit 100 provides fast detection oftransient events, and provides the signals SS, TR+, TR− in the same PWMswitching cycle during which the transient event occur. This is asignificant advance over other solutions that used comparators anddifferentiators created using op amp circuits to differentiate theoutput voltage to detect the transient event. Presently disclosedexamples provide significant transient detection speed improvement, andcertain implementations can detect transient events within a fewnanoseconds representing gate delays of a few gates in the phasedetector circuit 120. In addition, the disclosed circuits 100 provide alow power detection solution which cannot be achieved using high-speeddifferentiating op amp circuitry to achieve the detection speed whileusing a reasonable amount of current.

Referring also to FIGS. 5 and 6, the transient event detector circuit100 can be employed in any form of switching converter system, and canadvantageously be incorporated into a master controller and/or a PWMcontrol chip or IC. As noted above in FIG. 3, one possibleimplementation includes a switching converter control chip 301 having acontrol circuit 302 for operating an associated switching convertercircuit 320, as well as an on-board transient event detector thatconsumes the PWM signal from the control circuit 302 and generates oneor more of the signals SS, TR+, TR− for internal use or for use by anexternal multiphase converter master controller 340. The mastercontroller 340, in turn, can selectively control activation states(e.g., enabled or disabled) of one or more converter circuits 320 in amultiphase power conversion system. FIG. 5 shows another example of amultiphase DC-DC power conversion system 500, including an integernumber N DC-DC switching converter circuits 320, each connected by acorresponding output inductor LO1, LO2, . . . , LON to provide (whenenabled) a corresponding output current IO1, IO2, . . . , ION to drive ashared load 330. In this example, the individual switching convertercircuits 320 receive switching control signals SC1 and SC2 from acorresponding control circuit 302. The individual converter systems,referred to herein as “phases” are individually enabled by acorresponding slave control signal SCL1, SCL2, . . . , SCLN from amultiphase converter master controller circuit 340. The mastercontroller 340 in this case includes an integer number N outputs 148 toprovide the slave control signals SCL to the individual control circuits302. In one example, the slave control signals SCL are 2-state signalscausing the corresponding controller 302 to enable or disable operationof the corresponding switching converter 320. The individual controlcircuits 302 in this case provide their corresponding PWM signals PWM1,PWM2, . . . PWMN to a transient event detector circuit 100 as describedabove. In one example, the transient event detector circuit 100, thecontrol circuits 302 are stand-alone converter control ICs, and themaster controller 340 is a separate IC. In this case, the transientevent detector circuit IC 100 is connected in a given implementation tothe control circuits 302 and to the master controller 340 by appropriatecircuit board connections (not shown). FIG. 6 shows another system 600in which the transient event detector circuit 100 and the mastercontroller 340 are included in a single integrated circuitimplementation. In another alternate implementation, the mastercontroller circuitry 340, the transient event detector circuit 100 andthe single or multiple converter control circuits 302 can be provided ina single multiphase controller IC.

The above examples are merely illustrative of several possibleembodiments of various aspects of the present disclosure, whereinequivalent alterations and/or modifications will occur to others skilledin the art upon reading and understanding this specification and theannexed drawings. Modifications are possible in the describedembodiments, and other embodiments are possible, within the scope of theclaims.

The following is claimed:
 1. A circuit to detect transient events inswitching converter, comprising: a monostable multivibrator circuit,including: a signal input to receive a first signal having a risingedge, a falling edge, and a duty cycle representing an on-time of aswitching device of the switching converter in a given switching cycleof the switching converter, an output to provide an output pulse signalhaving a rising edge triggered by the rising edge of the first signal, afalling edge, and a voltage controlled pulse duration, and a controlinput to receive a voltage control signal to control the pulse durationof the output pulse signal; a phase detector circuit, including: a firstinput coupled with the output of the monostable multivibrator circuit toreceive the output pulse signal, a second input coupled with the signalinput of the monostable multivibrator circuit to receive the firstsignal, a first output to provide a first phase detector output signalin a first state in response to the falling edge of the first signallagging the falling edge of the output pulse signal, and a second outputto provide a second phase detector output signal in a first state inresponse to the falling edge of the first signal leading the fallingedge of the output pulse signal; a capacitor connected to the controlinput of the monostable multivibrator circuit; a charge pump circuitconfigured to selectively source a first current to the control inputwhen the first phase detector output signal is in the first state, toselectively sink a second current from the control input when the secondphase detector output signal is in the first state; and an outputcircuit to provide a status output signal in a first state when neitherof the first and second phase detector output signals is in the firststate, the output circuit providing the status output signal in a secondstate indicating a transient event in the switching converter inresponse to one of the first and second phase detector output signalsbeing in the first state.
 2. The circuit of claim 1, wherein the outputcircuit further includes: a first low pass filter circuit, including aninput coupled with the phase detector circuit to receive the first phasedetector output signal, and an output to provide a first filtered outputsignal having a first state when the first phase detector output signalis in the first state; a second low pass filter circuit, including aninput coupled with the phase detector circuit to receive the secondphase detector output signal, and an output to provide a second filteredoutput signal having a first state when the second phase detector outputsignal is in the first state; and a NOR gate with a first input coupledwith the output of the first low pass filter circuit, a second inputcoupled with the output of the second low pass filter circuit, and anoutput to provide the status output signal in the first state whenneither of the first and second filtered output signals is in the firststate, the NOR gate output providing the status output signal in thesecond state indicating a transient event in the switching converterwhen one of the first and second filtered output signals is in the firststate.
 3. The circuit of claim 2, wherein the output circuit providesthe first filtered output signal in the first state to representdetection of a transient event causing an increase in an output currentof the switching converter, and provides the second filtered outputsignal in the first state to represent detection of a transient eventcausing a decrease in the output current of the switching converter. 4.The circuit of claim 2, wherein the monostable multivibrator circuit,the phase detector circuit, and the charge pump circuit form a delaylock loop (DLL) circuit to align the falling edge of the output pulsesignal to the falling edge of the first signal in steady state operationof the switching converter; and wherein the DLL circuit has a bandwidthequal to a bandwidth of a control circuit operating the switchingconverter.
 5. The circuit of claim 1, wherein the monostablemultivibrator circuit, the phase detector circuit, and the charge pumpcircuit form a delay lock loop (DLL) circuit to align the falling edgeof the output pulse signal to the falling edge of the first signal insteady state operation of the switching converter; and wherein the DLLcircuit has a bandwidth equal to a bandwidth of a control circuitoperating the switching converter.
 6. An integrated circuit (IC),comprising: a transient event detector circuit, including: an input toreceive a pulse width modulation signal used to operate a switchingconverter, a delay lock loop (DLL) circuit to detect changes in a dutycycle of the pulse width modulation signal, and an output circuit toprovide a status output signal in a first state when no change in thepulse width modulation signal duty cycle is detected by the DLL circuit,the output circuit providing the status output signal in a second stateindicating a transient event in the switching converter in response tothe DLL circuit detecting a change in the pulse width modulation signalduty cycle; and a master controller to provide a control signal toselectively enable or disable a second switching converter to provide aload current to drive a load in response to receiving the status outputsignal in the second state.
 7. The IC of claim 6, further comprising acontrol circuit operating the switching converter, the control circuitincluding a modulator to generate the pulse width modulation signalaccording to a feedback signal to regulate an output voltage signal ofthe switching converter, and a driver circuit to generate a switchingcontrol signal to operate the switching converter according to the pulsewidth modulation signal.
 8. The IC of claim 6, wherein the DLL circuitincludes: a monostable multivibrator circuit to provide a pulse outputsignal having a first edge triggered by a first edge of the pulse withmodulation signal, and a second edge, the monostable multivibratorcircuit controlling a pulse duration of the pulse output signalaccording to a voltage control signal at a control input; a phasedetector circuit to provide first and second phase detector outputsignals according to a phase difference between the second edge of thepulse output signal and a second edge the pulse with modulation signal;a capacitor connected to the control input to provide the voltagecontrol signal to the monostable multivibrator circuit; a charge pumpcircuit configured to selectively source a first current to the controlinput to increase the voltage control signal when the first phasedetector output signal is a first state, and to selectively sink asecond current from the control input to decrease the voltage controlsignal when the second phase detector output signal is in a first state;and wherein the output circuit provides the status output signal in thefirst state when neither of the first and second phase detector outputsignals is in the first state, the output circuit providing the statusoutput signal in the second state in response to one of the first andsecond phase detector output signals being in the first state.
 9. The ICof claim 8, wherein the output circuit further includes: a first lowpass filter circuit, including an output to provide a first filteredoutput signal having a first state when the first phase detector outputsignal is in the first state; a second low pass filter circuit,including an output to provide a second filtered output signal having afirst state when the second phase detector output signal is in the firststate; and a NOR gate with a first input coupled with the output of thefirst low pass filter circuit, a second input coupled with the output ofthe second low pass filter circuit, and an output to provide the statusoutput signal in the first state when neither of the first and secondfiltered output signals is in the first state, the NOR gate outputproviding the status output signal in the second state indicating atransient event in the switching converter when one of the first andsecond filtered output signals is in the first state.
 10. The IC ofclaim 8, wherein the DLL circuit aligns the falling edge of the outputpulse signal to the falling edge of the first signal in steady stateoperation of the switching converter, and wherein the DLL circuit has abandwidth equal to a bandwidth of a control circuit operating theswitching converter.